Testing machine



Oct. 26 1926.

A AMSLER TESTING MACHINE Filed June 5 1924 [1e yen Z01 5% Patented'Dc t.26, 1926.

ALFRED AMSLER, OF SCHAFFHAUSEN, SWITZERLAND.

TESTING MACHINE.

Application filed .Tune 3, 1924, Serial No. 717,550, and in SwitzerlandApril 23, 1924.

The present invention relates to improvements in a ram which isparticularly adapted for carrying out fatigue tests on test pieces bysubjecting the latter to blows of the same -impact and following oneanother as quickly as possible and so often until a fracture of the'test piece occurs. The fatigue tests may be carried out with testpiecessubjected to bending, compression or 1 tensile stresses.

With known rams for carrying out longrun tests the force of thepercussion depends on the weight of the hammer and the velocity at whichthe testing machine of this i type may run is substantially dependent onthe speed of fall of the hammer. The velocity I of the known rams istherefore limited; and as in most cases several hundred thousands ofblows have to be exerted 0 during a long-run impact test, such tests eX-tend sometimes over weeks.

These drawbacks are overcome by the ram according to the presentinvention.

The ram according to the invention comprises a shaft rotating at auniform speed and provided with two crank pins arranged diametricallyopposite toleach other and a hammer moving in guides, the hammer beingalways maintained in contact with one 0 or the other of the crank pins,by the action of a spring except during the short period immediatelyafter the hammer reaches the test piece, whereby the hammer is movedtowards and awayfrom the test piece so that during each cycle the hammerimpactsonthe test piece with the same kinetic energy which is onlydependent on the mass of the hammer and on the eccentricity and rotatingspeed of the crank pins, th gravity 40 action of the hammer weight andthe frictional resistances of the latter being eliminated.

' Preferably means are provided in order to keep the test piece in sucha spaced relationship to the eccentricity of the crank pins that thetest piece is hit by the hammer following up one of the crank pins asthe hammer has attained its maximum speed whereupon the reboundinghammer is overtaken by the other'crank pin immediately after the impactand is returned into its initial position.

During the downward movement of the hammer the speed of the latter isequal to the instantaneous vertical speed of the contact point betweenthe crank pin and the part of -the ham1ner contacting with the crank pinand such speed is thus independent of other minor forces, such asfriction, or the force of gravity. The force of the spring must besufficient to maintain the hammer in contact with one of the crank pinswhichv for the time being is moving away from the hammer. -The kineticenergy dissipated on the test piece is, therefore, a function of thespeed of the shaft of the testing machine and of the vertical distancebetween the pane of the hammer when in the uppermost position and thepoint of impact on the test piece. At a given speed of the shaft and agiven eccentricity of the crank pins the hammer impacts with the samespeed and therefore with the same force On the test piece; the impactforce does not depend on the force of the springs, as is the case withknown testing machines for this purpose.

A suitable selection of the speed of the shaft, of the eccentricity ofthe two crank pins and of the force of the spring acting on the hammerenables to obtain any desired kinetic energy of the hammer and anynumber of blows wide range.

If the test piece subjected to impact tests were perfectly elastic thehammer would rebound with the same speed with which it hits on the testpiece. Owing to the imperfect elasticity of the test piece the hammeralways rebounds with a smaller speed. In order to avoid unfavorable,shocks occurring at the moment when the crank pin overtakes therebounding hammer it is advantageous to make the crank pins resilient byfixing the latter to a member which is adapted to carry out a relativedisplacement with respect to the driving shaft against a frictionalresistance, .the latter will have to be so adjusted that it is largeenough to lift the hammer. The shocks occurring between crank pins andhammer are resiliently taken up and cause only a small angulardisplacement between the member carrying the crank pins and the shaft.

A constructional example of the ram acperunit of time within a cordingto the present invention is illus- Fig. 1 is a front elevation of theram used to subject a test piece to compression stresses,

Fig. 2 is a vertical section along line IIII of Fig. 1.

Fig. 3 is a front elevation with parts broken away of the ram applied tosubject a test piece to bending stresses, whereby the hagimer is shownin its lowermost position, an

Fig. 4 is part of a front elevation of the ram in its application forsubjecting a test piece to tensile stresses.

Referring to the constructional example illustrated in the drawings 1denotes the hammer adapted to move up and down in the vertical directionin guides, for instance pr smatic guides 1. 2 designates the head and 5are mounted on a disc 6 loosely mounted on'the driving shaft and thedisc 6 is clamped in between the discs 7 and 8 which are pressed againsteach other by the spring 9 the pressure of which can be adjusted bymeans of the nut 9'. The friction thus generated between the discs 6, 7and 8 is the driving connection between the driving shaft 10 and therollers 4 and 5. The term crank pins used in this connection shall beinterpreted to include also eccentrics. To the driving shaft 10 on whichthe flywheel 11 is mounted, rotation at a uniform speed is imparted by a'motor not illustrated on the accompanying drawings. 12 and 13 denotehelical tension springs connected with their one ends to the traverse 3and with their other ends to the'frame of the apparatus, so that theycontinuously pull the hammer in the downward direction into con tactwith one or the other of the crank pins or rollers 4 and 5, so that thehammer follows during the rotation of the crank pins that crank pinwhich moves away from the hammer. Obviously compression springs actingon the top of the traverse may be used instead of the tension springs 12and 13..

In Fig. 3 of the drawings the hammer is Shown in a position in which thepane 2 4 has just got out of contact with the travjust touches. the testpiece 14 and the roller erse whilst between the roller 5 and thetraverse 3 a small clearance exists which must be of such a slze as topermit an appropriate deflection of the test piece. These conditions areobtained by a suitable dimensioning of the means determining theelevation of the test piece relatively-to the eccentricity of the crankpins. The test piece is hit immediately before the hammer has reachedits maximum speed." whereupon the rebounding hammer isovertaken by theroller 5 immediately after the impact and is lifted by this roller intoits uppermost position illustrated in Figs. 1 and 2, whereupon the cycleis performed anew the roller 4 effecting now the lifting of the hammerprevious to the next working stroke.

When a rupture of the test piece occurs or when the latter deflectsbeyond a predetermined amount the hammer abuts against a stop 15 (Fig.2) which limits its downward stroke. Thereupon a device is actuatedwhich secures the hammer in its uppermost position and causes the ram tobe cut out of action. -This device is illustrated in Fig. 1 andcomprises a pawl 24 turnable about a pivot 25 and adapted to enter withits upper end .into a notch 26 provided on the hammer. The lower end 27of the pawl is pressed against a tooth 28 by the action of the spring29. The tooth 28 is provided on a one armed lever 30 pivoted at 31 andheld by the action of a spring 32 against a stop pin 33 so that the freeend of the lever 30 projects into the path of the hammer when the lattermoves beyond the downward stroke determined by the test piece in case ofrupture of the latter. In this case the hammer causes a turning of thelever 30 so that the tooth is withdrawn and the pawl 24 released; thelatter is then turned towards the hammer and enters the notch 26 of thehammer which has been moved meanwhile into its uppermost position and isthereby held in this position. In order to cut out the motor driving theram a contact spring 34 is provided on the pawl which co-operates with astationary contact 35 whereby an electric circuit is closed whichoperates in a well known manner a cut-out switch for the motor.

A counter 16 provided with an arm 21 against which a pin 22 provided onthe hammer strikes registers the number of im.- pacts of the hammerwhich have been necessary for effecting the destruction of the testpiece.

Fig. 4 illustrates the ram in its application for subjecting the testpiece to tensile stresses, whereby the uppermost transverse portion 23of the hammer hits against a sleeve 19 screwed to the lower end of thetest piece whilst a similar sleeve 20 screwed to the upper end of thetest piece rests in the top portion 36 of the frame.

When a test piece is subjected to bending stresses the test piece has tobe turned either continuously orintermittently about its axis so-thatthe blows of the hammer act in a uniform manner on the wholecircumference of the test piece. A device foretfecting the turning ofthe test piece is illustrated in Figs. 2 and 3 of the accompanyingdrawings. The turning motion is derived from a worm 37 on thedrivingshaft 10 and is transmitted by the intermediary of a worm wheel 88, anupper grooved pulleyv39, a cord 40, a lower grooved pulley 41 and acoupling 42 cooperating with a pin 43 passing transversely through thetest piece 14. The latter is held in position on its support 44 by meansof the resilient straps 45 and 46.

Obviously the hammer of the ram could be guided in a different directionand it could work even from below againstthe parting test piece as thekinetic energy of the hammer is independent of the gravity or it couldbe guided along a circular path without devention.

. I claim:

1. In a ram particularly adapted for carrying out long-run impact testson test bars, the combination with a driving shaft rotating at a uniformspeed, of members eccentric to said shaft and diametrically oppositeeach other and rotating about the axis of said shaft, a hammerco-operating with said members, guide means for said hammer and springsin operative connection with said hammer and maintaining the lattersubstantially constantly in contact with one or the other of saidmembers whereby the hammer is moved towards and away from the test pieceand'hits the latter with the same force which only depends on the massofthe hammer, on the eccentricity and the speed of rotation of saidmembers. on the gravity action of the hammer weight and on itsfrictional resistancesand the force of the springs.

2. In a ram particularly adapted for carrying out long-run impact testson test bars, the combination with a driving shaft rotating at a uniformspeed, of members eccentric to said shaft and diametrically oppo siteeach other and rotating about the axis of said shaft, ahammerco-operating with said members, guide means for said hammer,springs in an operative connection with said hammer and maintaining thelatter substantially constantly in contact with one orthe other of saidmembers, whereby the hammer is moved towards and away from the testpiece, and means adapted to hold the test piece in such a position withrespect to the eccentricity of said membersthat the test piece is hit bythe hammer following one of said members as the hammer approaches itsmaximum speed whereupon the rebounding hammer is overtaken by the otherof said members and is returned into its initial position.

3. In a ram particularly'adapted for carrying out long-run impact testson test bars, the combination with a driving shaft rotatfrom the spiritof the present inand is independent ing' at a uniform speed, of memberseccentric to said shaft and diametrically opposite each other androtating about the axis of said shaft, a hammer co-operating with saidmembers provided with a facing with which said members cooperate,vertical guide means for said hammer, springs in opera tive connectionwith said hammer and maintaining the latter substantially constantly incontact with one or the other of said members, whereby the hammer ismoved towards and away from the test piece, and means adapted to holdthe test piece in such a position with respect to the eccentricity ofsaid members that the test piece is hit by the hammer following one ofsaid members as the hammer approaches its maximum speed whereupon therebounding hammer is overtaken by the other of said members and isreturned into its initial position.

4. In a testing machine, a reciprocable hammer, eccentric rotating meansfor determining the speed of said hannner, means to maintain the hammerin contact with the speed determining means during its operative stroke,means for supporting a test piece to be struck by said hammer as thehammer approaches its maximum speed, whereby the hammer is supported andcontrolled during movement against the testpiece by said eccentricrotating means.

5. In a ram particularly adapted for carrying out long-run impact testson test bars, the combination with a driving shaft rotating at a uniformspeed, of members ar ranged eccentrically to said shaft anddiametrically' opposite each other, a frictional driving connect-ioninterposed between said members and said shaft to cause said members torotate about the axis of said shaft, a hammer co-operating with saidmembers, guide means for said hammer and springs in operative connectionwith said hammer and maintaining the latter substantially constantly incontact with one or the other of said members whereby the hammer ismoved towards and away from the test piece and hits the latter with thesame force which only depends on the mass of the hammer, on theeccentricity and the speed of r0- tation of said members, and isindependent 'on the gravity action of the hammer weight and on itsfrictional resistances.

6. In a ram particularly adapted for carrying out 1ong-run impact testson test bars, the combination with a driving shaft rotating at a uniformspeed, of members arranged eccentrically to said shaft and diametricallyopposite each other, an adjustable frictional driving connectioninterposed between said members and said shaft to cause said members torotate about the axis of said-shaft, a hammer co-operating with saidmembers, guide means for saidhammer and springs in operative connectionwith said hammer and maintaining the latter substantially constantly incontact with one or the other of said members whereby the hammer ismoved towards and away from the test piece and hits the latter with thesame force which only depends on the mass of the hammer, on the meansfor said hammer, springs in operative connection with said hammer andmaintaining the latter substantially constantly in contact with one orthe other of said members, whereby the hammer is moved towards and awayfrom the test piece, and means adapted to hold the test piece in such aposition with respect to the eccentricity of said members that the testpiece is hit by the hammer following one of said members as the hammerreaches its maximum speed whereupon the rebounding hammer is overtakenby the other of said members and is returned into its initial position,and means operated by said hammer and adapted to lock the latter in afixed position when the operative stroke of the'hammer undulyincreasesbeyond a predetermined limit. d

8. In a ram particularly adapted for carrying out long-run impact testson test bars,

the combination with a driving shaft rotating at a uniform speed, ofmembers arranged eccentrically to said shaft and diametrically oppositeeach other, an adjustable frictional driving connection between saidmembers and said shaft to cause said members to rotate about the axis ofsaid shaft, a hammer co-operating with said members, a head on one endof said hammer co-operating with a test piece when subjecting the latterto upsetting or bending stresses and the other end of said hammer beingadapted for cooperating with a test piece when subjecting the latter totensile stresses, guide means for said hammer springs in operativeconnection with said hammer and maintaining the latter substantiallyconstantly in contact with one or the other of said members, whereby thehammer is moved towards and away from the test piece, and means adaptedto hold the test piece in such a position with respect to theeccentricity of said members that the test piece is hit by the hammerfollowing one of said membersas the hammer reaches its maximum speedwhereupon the rebounding hammer is overtaken by the other of saidmembers and is returned into its initial position, and means operated bysaid hammer and adapted to lock the latter in a fixed position when theoperative stroke of the hammer unduly increases beyond a predeterminedlimit.

9. In a ram particularly adapted for carrying out long run tests on testbars, the combination with a driving shaft and members eccentric to androtated by said shaft; of a hammer, spring-means to urge the hammer intocontact with said members, said members releasin said hammer as itapproaches its maxlmum impact speed when it strikes a test piece with aforce that is independent of the force of said springmeans.

In testimony whereof I afiix my signatui e.

-DR. ALFRED AMSLER.

